There are many types of knives, both automatic and manual, that utilize trigger-activated mechanisms that allow an implement to be moved between a folded position in which the implement is safely stowed in the tool handle, and an extended position in which the implement is ready for work. Of course, automatic versions of these knives include spring mechanisms that automatically drive the blade into the open position; manual knives require the blade to be moved manually from closed to open. The knife handle typically has two opposed handle portions defining a blade-receiving groove. A blade pivots on a shaft attached to the handle such that in a folded position the blade is stowed with the cutting portion of the blade safely in the groove, and such that in an extended position the blade is extended away from the handle, ready for use. The trigger mechanism controls movement of the blade from the closed to the open position—that is, when the blade is closed and the trigger is actuated, the blade may be moved either automatically or manually to the open position.
As noted, automatic opening knives include some kind of a spring-like or spring-driven mechanism that urges a blade from the closed position to the open position. In the closed position the blade must be locked against the constant opening force of the spring applied to the blade. Typical springs include spirally wound torsion springs that are wrapped around the pivot axis of the blade and which on one end engage the pivot pin, handle, liner or some other fixed, non-rotational structure, and on the other engage the blade. Other designs use compression springs and still others use extension springs and spiral wound flat springs and leaf springs. Many automatic opening mechanisms utilize or adapt the well-known sear type of design. Regardless of the particular mechanism used, when the locking mechanism is released, the spring forces the blade into the open position.
Preferably, push-button knives of the kinds described herein also include a locking mechanism that locks the blade in the open position. There are many designs for locking mechanisms to accomplish this task. Generally speaking, when the knife blade pivots into the open position, the blade's pivotal movement is stopped with a transverse blade stop pin housed in the handle. The locking mechanism is included to prevent the blade from pivoting back from the open into the closed position until the user purposefully closes the knife.
One common type of locking mechanism is a “liner lock.” This kind of mechanism relies upon a resilient lever formed as part of a handle liner. When the blade is pivoted to the open or extended position, the resilient lever engages a cooperatively formed ramp on the blade and thereby locks the blade in the open position.
Two separate patents describe different types of automatic knives that use push-button release mechanisms: U.S. Pat. No. 5,822,866 and U.S. Pat. No. 7,278,213. Both of these patents are described briefly below. Both are owned by the assignee of the present invention and both are incorporated herein by this reference.
The automatic opening knife detailed in the '866 patent relies on a push button bolt mechanism that includes a locking body that has a cylindrically tapered side wall portion. When the blade is extended to the open position, the tapered side wall portion of the locking body is urged by a compression spring into a locking position in which the locking body wedges between an engagement surface on the blade and a bore in the handle to lock the blade in the open position.
The locking mechanism for automatic knives disclosed in U.S. Pat. No. 7,278,213 also relies upon a push-button type of bolt. The trigger mechanism has a bolt that extends transverse to the handle. When an exposed portion of the trigger mechanism is depressed the bolt moves laterally in the knife handle. Once the bolt clears the tang of the blade, the blade disengages from the bolt and is swung to the open position by a spring.
The release buttons, also known as lock buttons, or “bolts” described in the two patents just mentioned are critical components of the knives since they control the opening mechanisms, and also lock the blade in both the open and closed positions. The bolts are defined by a trigger button end that is exposed to the outside of the handle, a tapered locking end at the opposite end, which is housed internally in the handle, and a central, axial and cylindrical shaft or shank interconnecting the two ends. When the button end is pushed, the bolt moves laterally in the handle. As the bolt moves, the tang of the blade, which is driven rotationally by a coil spring, has enough clearance to move past the bolt because the central shank is relatively small in diameter, thereby allowing adequate clearance and allowing the blade to rotate to the open position. Once the blade is in the open position, its rotation having been stopped by a stop pin, the pressure on the bolt is released and the tapered locking end of the bolt engages a portion of the tang, thereby locking the blade in the open position and preventing movement of the blade to the closed position.
There is a need therefore for an improved and more robust release button mechanism for use in a knife that relies upon a push button type of release and locking mechanism.
The present invention relates to an improved design for a release button or bolt for use in a push-button type release folding knife, in which the button serves to control the locking/opening mechanism, and to lock the blade in either the open or closed positions, or both positions.